pom/transpose_midi.py

#! /usr/bin/env python3

# This script takes a directory of MIDI files and transposes them between -max and +max semitones
# It was intended for the P909 dataset
# It will create a directory of images for each MIDI file, where each image is a frame of the MIDI file

import os
import sys
import pretty_midi
from multiprocessing import Pool, cpu_count, set_start_method
from tqdm import tqdm
from control_toys.data import fast_scandir
from functools import partial
import argparse
from copy import deepcopy


def transpose_midi(args, midi_file):
    #print("midi_file = ",midi_file)
    if '_transposed_' in midi_file: return # don't transpose files that have already been transposed
    midi_save = pretty_midi.PrettyMIDI(midi_file)
    for transpose_by in range(-args.transpose, args.transpose+1):
        midi = deepcopy(midi_save)
        if transpose_by == 0: continue
        for instrument in midi.instruments:
            for note in instrument.notes:
                note.pitch += transpose_by
        midi.write(midi_file.replace('.mid', f'_transposed_{transpose_by}.mid'))
    return

if __name__ == '__main__':
    p = argparse.ArgumentParser(description=__doc__,
                                formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    p.add_argument('-t','--transpose', type=int, default=0, help='transpose by this maximum number of semitones (+/-)')
    p.add_argument('--start-method', type=str, default='fork',
                   choices=['fork', 'forkserver', 'spawn'],
                   help='the multiprocessing start method')
    p.add_argument('--skip-versions', default=True, help='skip extra versions of the same song')
    p.add_argument("midi_dirs", nargs='+', help="directories containing MIDI files")
    args = p.parse_args()
    print("args = ",args)

    set_start_method(args.start_method)
    midi_dirs = args.midi_dirs

    if os.path.isdir(midi_dirs[0]):
        midi_files = []
        for mdir in midi_dirs:
            m_subdirs, mf = fast_scandir(mdir, ['mid', 'midi'])
            if mf != []: midi_files = midi_files + mf
    elif os.path.isfile(midi_dirs[0]):
        midi_files = midi_dirs

    if args.skip_versions: 
        midi_files = [f for f in midi_files if '/versions/' not in f]
    #print("midi_files = ",midi_files) # just a check for debugging
        
    # transpose all the midi files
    if args.transpose != 0:
        transpose_one = partial(transpose_midi, args)
        with Pool(cpu_count()) as p:
            list(tqdm(p.imap(transpose_one, midi_files), total=len(midi_files), desc='Transposing MIDI files'))

    print("Finished")